1. Field of the Invention
The present invention relates to a method and apparatus for performing a resist process on an object to be processed such as a semiconductor wafer (to be referred to as a wafer hereinafter) or an LCD substrate.
2. Description of the Related Art
Generally, in the process of manufacturing a semiconductor device or a liquid crystal display element, a series of processes are performed as follows. That is, an object to be processed such as a wafer or an LCD substrate is arranged on a spin chuck capable of high-speed rotation, and a photoresist containing a photosensitive material is coated on the object to be processed while rotating the object to be processed at a high speed. A circuit pattern is transferred to the photoresist by using a photolithographic technique, and a developing process is performed on the resultant photoresist. In this developing process, a developing solution as a process solution is supplied onto the photoresist to which the circuit pattern is transferred. Thereafter, the developing solution is washed away, and a cleaning solution (rinse solution) for cleaning the surface of the wafer is supplied.
In the developing process, when the photoresist which is exposed and cannot be dissolved with respect to the developing solution contacts the developing solution, the photoresist swells (i.e., its volume increases). Then, when the swelling photoresist contacts the rinse solution, the developing solution is washed away, and the photoresist shrinks. Therefore, if the width of a circuit pattern transferred to the photoresist is small, a bridge is undesirably formed on the circuit pattern when the photoresist swells. Since the photoresist swells and shrinks, a stress is applied to the photoresist.
A polyimide-based resist, for example, has a relatively high viscosity. When the polyimide-based resist is used as an insulating interlayer, this resist is formed to have a large film thickness of about 10 .mu.m. In this case, the conventional developing method requires a long period of time for a developing process, resulting in a decrease in throughput. In order to solve this problem, it may be considered to increase the supply amount of a developing solution. Even if the supply amount of the developing solution is increased, the throughput does not increase so much, and the consumption amounts of the developing solution and a rinse solution are increased.
In the case of using a rectangular LCD substrate as an object to be processed, since the LCD substrate is relatively large, a developing solution supply nozzle (process solution supply means) for supplying a developing solution is arranged to be opposite to the LCD substrate so as to move the nozzle relative to the LCD substrate in the developing process. Since axial vibrations tend to occur during rotation of a spin chuck, the spin chuck is rotated by the rotating shaft of the spin chuck and a driving motor through a transmission means such as a belt or a chain. When a developing solution is to be supplied to the developing solution supply nozzle, a compressed nitrogen (N.sub.2) gas, for example, is supplied into a developing solution tank connected to the developing solution supply nozzle through a developing solution supply pipe.
When the developing process is performed by using the resist processing apparatus having this arrangement, the developing solution supply nozzle is moved relative to the LCD substrate having the photoresist to which the circuit pattern is transferred, and the developing solution is supplied onto the photoresist in a film-like manner to perform development for a predetermined time. Thereafter, while rotating the spin chuck at a high speed, a rinse solution such as deionized water or distilled water is supplied onto the LCD substrate to wash away the developing solution.
In the above resist processing method, however, the developing solution supply nozzle is moved relative to the LCD substrate. For this reason, if positioning of the developing solution supply nozzle with respect to the LCD substrate is inaccurate, the developing solution is not coated on the end portion of the LCD substrate. A film of the developing solution formed on the photoresist becomes nonuniform, resulting in a decrease in yield. Since the axial vibrations occur during rotation of the spin chuck, a seal portion of the rotating shaft wears greatly, and this rotational vibrations may make the thickness of the film of the developing solution nonuniform, shortening the service life of the apparatus.
In addition, since the developing solution is supplied under pressure by the N.sub.2 gas or the like to be supplied onto the LCD substrate, the N.sub.2 gas is dissolved in the developing solution to form bubbles, and the bubbles are supplied onto the LCD substrate together with the developing solution. The bubbles undesirably cause development nonuniformity. Air may enter from apertures of the developing solution supply nozzle into the nozzle. In this case, the air entering into the nozzle also becomes bubbles, and the bubbles are also supplied onto the LCD substrate, causing the development nonuniformity.